Link between window parameter and sample rate

[andiandi13]

I don't understand something.

I have two audio tracks. The destination track begins 4950ms after the source track, so I shifted my subs like this in the first place :

sushi --src 001.wav --dst 002.wav --script 001.srt

However, the first seconds before the intro are too late in the subs (the rest of the subs after the intro are perfect).

So after reading the wiki, I understood that increasing the window would help.

I tried :

sushi --src 001.wav --dst 002.wav --window 15 --script 001.srt

But the resulting .ass file is the exact same.

So I just took the line from the wiki, adding sample rate, without knowing what I was doing :

sushi --src 001.wav --dst 002.wav --window 15 --sample-rate 24000 --script 001.srt

And now the shifted subtitle file is perfectly synced in the beginning. So :

1) Why do I have to specify a sample rate, what's it's role ?
2) Does it have to be 24KHz everytime ?
3) Also, about the window, I wanted to know what's the unit ? window 15 = 15ms ? 15seconds ?

[qgustavor]

1. When using a .wav input you need to specify a sample rate otherwise it will use a default sample rate of 12000 Hz.
2. If you use a .wav input it needs to match the sample rate of your input, otherwise it will convert your input to wav using the sample rate specified in --sample-rate defaulting to 12000 Hz.
3. In at least two parts of the code, here and here, appears that window is measured in seconds.

[andiandi13]

@qgustavor Thanks a lot for these informations, it's really helpful !

Can you just specify what you mean in the second point ?
If I understood, if I have a 48 KHz WAV as an input, I have to write --sample-rate 48000 or it'll convert it to 12000 right ?